Voice coil motor (VCM) actuators creating a one-directional (single-axis) stroke can be used for camera autofocus (AF), multi-axis optical image stabilization (OIS) or multi-axis haptic feedback applications. In case of multi-axis applications, a respective number of VCM actuators can be arranged accordingly.
Current VCM systems with higher performance employ Hall sensors for the position feedback of the moving part, which includes, e.g. coil and lens barrel in case of an AF camera module. This construction has some advantages, such as low current in idle stage as well as fast AF response. However, this setup requires additional elements, such as permanent magnets and Hall sensor ICs.
An alternative way is to use a spring-preloaded VCM with an excursion, which approximately depends on a linear restoring force that allows, after calibration, linear control via a current source. In general, this setup is used for more economic solutions. The drawback of this solution resides in increased power consumption as well as limited AF speed, which is limited by a resonance frequency of the mass-spring system.